1. Field of the Invention
This invention relates to a solderless termination system for contact elements in electrical connectors. In particular, it relates to such a system in which thin conductive sheet metal is formed into a wire receptacle adapted for rupturing the insulation of a wire upon insertion and engaging and holding the underlying conductor.
2. Description of the Prior Art
Multiple-wire termination systems have come into extensive use in the government electronics and telecommunications industries. These termination systems are widely used in commercial connectors having fifty contact members, more or less, arranged in parallel adjacent rows. The contact elements are recessed into elongated passages formed in a dielectric contact mount and are of sheet metal shock having one end thereof formed into a U-shaped wire receiving channel or receptacle. Termination systems of this type are used for splicing wires as well as for terminating wires in connectors.
Originally most such termination systems were of the type in which bare conductors are soldered into U-shaped channels of conductive sheet metal. These solder-type connectors required high-temperature dielectric materials and substantial manual labor or elaborate machinery for inserting and soldering the conductors into place. As a result, a number of solderless versions of the channel-type termination have been devised, some of which have proven capable of meeting the rigid performance demands normally placed on such terminations. Particularly in high density applications, severe design and performance specifications must be met. For example, contact resistance must be minimized and must remain quite constant over a range of environmental variables and time. Also, physical strength and economy of manufacture must be maximized.
Ease of manufacture has dictated the use of thin conductive sheet metal as the material for a large number of termination systems of both the solder and solderless type. This material, typically cadmium bronze of 0.006 inches thickness, can be rapidly fed in a long continuous ribbon through the desired stamping and forming operations. Manual steps are few, if any, and metal waste can be carefully controlled. Several solderless termination systems heretofore known in the art have incorporated the thin, relatively sharp edges possessed by the metal stock itself as cutting edges for piercing and separating the insulation from the conductor as it is inserted into the termination end of the contact element. The metal is easily formed into opposing blades or jaws converging into the channel to define a lead-in area to provide convenient positioning and gradual gripping of the wire upon insertion.
For example, the copending application Ser. No. 443,678 of William McKee and Roy Witte discloses a termination system made from thin conductive sheet metal and having sidewall portions which are formed in and slit to define a tapered lead-in area at the upper entrance to the channel. The lead-in area has exposed metal edges which effectively pierce and separate the insulation from the conductor upon its insertion into the channel. Between the lead-in area and the vertical contact wiping surfaces is a gradual transition area that results from coining the inner edges of the formed-in sides.
Solderless termination systems of the type described above are effective in piercing and separating the insulation from insulation covered conductors by virtue of the sharp cutting edges which they possess in the lead-in area of the channel. However, the sharpness of the cutting edges presents a hazard to wires which are inserted slightly off-center of the channel in that severe scoring or cutting of the underlying conductor can take place before final contact is achieved. Even if the conductor remains axially intact, the effective point-contact area, as well as the gripping pressure between the jaws and the conductor, can be seriously diminished. In particular, the termination systems described above have severe limitations in connectors for terminating multiple-strand insulated wires. The individual conductors or strands found in such wire are extremely small in size and are easily pierced or broken unless adequate precautions are taken. Furthermore, the strands, by their very nature, move independent of one another and, as such, are collectively more easily deformed upon insertion into the channel than is a solid conductor of comparable guage. As a result, the conductor-to-contact pressure of the termination is substantially less than for solid wire terminations.
The termination system of the present invention overcomes the aforesaid limitations residing in the prior art devices in that it operates without the use of flat, sharp cutting edges which can score and damage solid conductors or sever the individual strands of stranded wire.